When a photovoltaic panel or laminate is exposed to direct or diffuse light, a lethal voltage potential may be present. In the United States the possible voltage could be as high as 600 volts, while in Europe and the rest of the world this voltage could approach a kilovolt.
Because of the potential danger from electrical shock, solar system installers take a large guard band (or safety margin) to make sure the voltages don't cross the 600V or 1000V limits in the United States and the European Union, respectively. That limitation inhibits them from installing more solar panel modules, often referred to as “modules” or “panels,” in series to reduce the cost of combiner boxes or string inverters. When solar modules are connected in series or in mesh configurations, there can be a problem in which weaker modules not only produce less energy, but also affect other modules' capabilities to deliver energy in the same string or wiring section.
Also, potential danger from these high voltages may exist in various types of situations. For example, first responders, solar array installers, and maintenance personnel operating near solar arrays can be exposed to dangerous or lethal voltages. The danger can be even higher if certain wires are disconnected through theft, vandalism, accident, natural forces, or other causes. To protect first responders, solar array installers, and maintenance personnel, solar arrays can be turned off in an emergency. However, the systems used to turn off a solar array in an emergency may sometimes be damaged or disabled by the emergency (e.g., fire).